Joint structure and manufacturing method thereof

ABSTRACT

A joint structure includes a first member configured to be connected rotatably to a mating member, and a second member configured to be connected rotatably to an actuator for driving the mating member. Each of the first and second members has one or more ridge portions that extend circumferentially along an outer peripheral surface. The joint structure further includes a core shaft connecting the first member and the second member, and a covering member provided tightly thereon to cover the core shaft, the one or more ridge portions of the first member, and the one or more ridge portions of the second member.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims the benefit of priority fromJapanese Patent Application Serial No. 2021-140373 (filed on Aug. 30,2021), the contents of which are hereby incorporated by reference in itsentirety.

TECHNICAL FIELD

The present disclosure relates to a joint structure and a manufacturingmethod thereof.

BACKGROUND

In a composite link described in U.S. Pat. No. 6,324,940 (“the '940Patent”), a fitting is fixed on each end of the tube having a squarecross section, and resin impregnated fiber is wound over the endfittings and tube. Each end of the tube is inserted into the fitting.

In the composite link of the '940 Patent, the resin impregnated fiber iswound up to the tip of the joint so that the joint does not come offfrom the tube. Instead of winding the resin impregnated fiber to the tipof the joint, it is conceivable to fasten the joint to the tube using afastener. It is desired to connect the tube and the joint without usinga fastener or the like.

SUMMARY

One aspect of the disclosure provides a joint structure. The jointstructure includes: a first member configured to be connected rotatablyto a mating member, the first member having one or more ridge portionsthat extend circumferentially along an outer peripheral surface; asecond member configured to be connected rotatably to an actuator fordriving the mating member, the second member having one or more ridgeportions that extend circumferentially along an outer peripheralsurface; a core shaft connecting the first member and the second member;and a covering member provided tightly thereon to cover the core shaft,the one or more ridge portions of the first member, and the one or moreridge portions of the second member.

Another aspect of the disclosure provides a method of manufacturing ajoint structure. The joint structure includes: a first member configuredto be connected rotatably to a mating member, the first member havingone or more ridge portions that extend circumferentially along an outerperipheral surface; a second member configured to be connected rotatablyto an actuator for driving the mating member, the second member havingone or more ridge portions that extend circumferentially along an outerperipheral surface; a core shaft having a first end portion and a secondend portion; and a covering member provided tightly thereon to cover thecore shaft, the one or more ridge portions of the first member, and theone or more ridge portions of the second member. The method includes:covering an outer peripheral surface of the core shaft with the coveringmember; inserting the first member into the covering member to connectthe first member to the first end portion and inserting the secondmember into the covering member to connect the second member to thesecond end portion; and heating the covering member to cure while thecovering member tightly contacts the core shaft, the one or more ridgeportions of the first member, and the one or more ridge portions of thesecond member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a part of a wing having a flight controlsurface drive device related to an embodiment installed thereon.

FIG. 2 is a side view of the driving unit related to the embodiment.

FIG. 3 is a perspective view of a joint structure related to theembodiment.

FIG. 4 is a plan view of the joint structure related to the embodiment.

FIG. 5 is a sectional view of the joint structure related to theembodiment.

FIG. 6 illustrates a connecting portion between a second member on theleft side of the joint structure related to the embodiment and a coreshaft.

FIG. 7 illustrates a connecting portion between a second member on theright side of the joint structure related to the embodiment and a coreshaft.

FIG. 8 illustrates a connecting portion between a first member on theleft side of the joint structure related to the embodiment and a coreshaft.

FIG. 9 illustrates a connecting portion between a first member on theright side of the joint structure related to the embodiment and a coreshaft.

FIG. 10 is a flow chart showing a method of manufacturing the jointstructure related to the embodiment.

FIG. 11 illustrates a state in which the core shafts of the embodimentare connected to each other with a connecting jig.

FIG. 12 illustrates a state in which the core shaft of the embodiment iscovered with a covering member and illustrates a cut portion of the cureshaft.

FIG. 13 illustrates a state in which the connecting jig is removed fromthe core shaft covered with the covering member related to theembodiment.

FIG. 14 illustrates a state in which a first member and a second memberare connected to a left core shaft covered with the covering memberrelates to the embodiment.

FIG. 15 illustrates a connected state between the first member, thesecond member, and a link main body on the left side of the jointstructure related to the embodiment.

FIG. 16 illustrates a state in which the first member and the secondmember are connected to a right core shaft covered with the coveringmember relates to the embodiment.

FIG. 17 illustrates a connected state between the first member, thesecond member, and the link main body on the right side of the jointstructure related to the embodiment.

FIG. 18 illustrates a state in which the link main body of the jointstructure related to the embodiment is bent by a jig.

FIG. 19 illustrates a connected state between the first member, thesecond member, and the core shaft on the left side of the jointstructure of the modified example.

FIG. 20 illustrates a connected state between the first member, thesecond member, and the core shaft on the right side of the jointstructure of the modified example.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

An embodiment of a flight control surface drive device including a jointstructure will be described with reference to FIGS. 1 to 18 . Note that,in FIGS. 1 and 2 , some part of a connecting structure between theflight control surface drive device and a flight control surface may beomitted for convenience.

As shown in FIG. 1 , a flight control surface drive device 1 is providedon a wing 100 of an aircraft. The flight control surface drive device 1drives a flight control surface 101 of the wing 100 of the aircraft. Theflight control surface 101 may include an aileron, a rudder, anelevator, or other control surfaces of aircrafts. The flight controlsurface driven by the flight control surface drive device 1 may includesa flap, a spoiler and the like.

The flight control surface drive device 1 includes an actuator 10 and areaction link 20. The actuator 10 drives the flight control surface 101.The reaction link 20 supports a reaction force from the flight controlsurface 101 when the flight control surface 101 is driven by theactuator 10. The reaction link 20 may be an example of aircraft reactionlinks. The reaction link 20 is a joint structure in which a plurality ofmembers are joined to each other.

As shown in FIG. 2 , the actuator 10 rotates the flight control surface101 relative to the wing 100. The wing 100 has a support portion 102.The flight control surface 101 has a connection shaft 103. The actuator10 is connected to the support portion 102 and the connection shaft 103.The flight control surface 101 has a fulcrum shaft 104. The fulcrumshaft 104 supports the flight control surface 101 rotatably relative tothe wing 100. The actuator 10 causes the flight control surface 101 torotate about the fulcrum shaft 104. The actuator 10 is a hydrauliclinear actuator. The actuator 10 includes a cylinder 11 and a rod 12.When a hydraulic oil is supplied to and drained from the cylinder 11,the rod 12 reciprocates in the axial direction thereof. The actuator 10may also be an electromechanical linear actuator including an electricmotor and a ball screw mechanism. A distal end of a rod 12 is rotatablyconnected to the connection shaft 103. That is, the actuator 10 isdirectly connected to the flight control surface 101. Alternatively, thedistal end of the rod 12 may be connected to a horn arm (not shown)connected to the flight control surface 101. That is, the actuator 10may also be indirectly connected to the flight control surface 101.Here, the flight control surface 101 corresponds to a mating member. Thefulcrum shaft 104 corresponds to a rotation shaft.

As shown in FIG. 1 , the actuator 10 includes a connecting portion 13.The connecting portion 13 is provided on a side of the cylinder 11opposite to a side thereof from which the rod 12 protrudes. Theconnecting portion 13 is connected with the support portion 102. Theconnecting portion 13 may include a shaft 13A extending orthogonally tothe axis of the rod 12. The reaction link 20 is connected with the shaft13A.

The reaction link 20 is rotatably connected to the fulcrum shaft 104 andthe shaft 13A of the connecting portion 13. When the actuator 10 drivesthe flight control surface 101, the reaction link 20 may prevent theload applied on the flight control surface 101 from directly impactingthe stationary wing 100.

Next, a description is given of an operation of the flight controlsurface drive device 1.

A hydraulic system (not shown) for supplying a hydraulic oil to theactuator 10 in accordance with instructions from a flight controller(not shown) is provided. The hydraulic oil may be supplied to anddrained from the cylinder 11 of the actuator 10 as the hydraulic systemworks. This causes the rod 12 to protrude from or retract into thecylinder 11 as shown in FIG. 2 , and thus the flight control surface 101connected to the rod 12 via the connection shaft 103 turns about thefulcrum shaft 104. The reaction link 20 supports the shaft 13Arotatably. The reaction link 20 receives, from the flight controlsurface 101, a reaction force generated when the flight control surface101 is driven by the actuator 10.

Next, the constitution of the reaction link 20 will now be describedwith reference to FIGS. 2 to 9 .

Referring to FIGS. 2 and 3 , the reaction link 20 includes a head 30, apair of bushes 40, and a pair of link main bodies 50. The head 30 isrotatably connected to the fulcrum shaft 104. The head 30 has a throughhole portion 38 through which the fulcrum shaft 104 penetrates. Thebushes are rotatably connected to the actuator 10. The bushes 40 eachhave a through hole 41 through which the shaft 13A penetrates. The linkmain body 50 connects the head 30 and the bush 40. The head 30corresponds to a first member. The bush 40 corresponds to a secondmember.

As shown in FIGS. 4 and 5 , the reaction link 20 has a bifurcatedY-shape and includes the pair of bushes 40 and the pair of link mainbodies 50. The bush 40 on the left side in the drawing is referred to asa first bush 40A, and the bush 40 on the right side in the drawing isreferred to as a second bush 40B. The link main body 50 on the left sidein the drawing is referred to as a first link main body 50A, and thelink main body 50 on the right side in the drawing is referred to as asecond link main body SOB. The first bush 40A is connected to the firstlink main body 50A. The second bush 40B is connected to the second linkmain body SOB. The reaction link 20 has a bent portion 51 in the linkmain body 50. A portion of the first link main body 50A and a portion ofthe second link main body SOB from the bent portion 51 to the bush 40extend in parallel to each other. The actuator 10 is disposed betweenthe first link main body 50A and the second link main body SOB (see FIG.1 ). The shape of the reaction link 20 may be a linear shape or J-shapeinstead of the Y-shape. When the shape of the reaction link 20 is thelinear shape or J-shape, the reaction link 20 includes a single bush 40and a single link main body 50.

The link main body 50 includes a core shaft 60 and a covering member 70.The core shaft 60 connects the head 30 and the bush 40. The core shaft60 is a cylindrical member. An end portion of the core shaft core 60preferably has a cylindrical shape, but portions of the core shaft 60other than the end portion may not be cylindrical. The covering member70 covers a first connecting portion 52 between the head 30 and the coreshaft 60 and a second connecting portion 53 between the bush 40 and thecore shaft 60. The covering member 70 covers the core shaft 60 inaddition to the first connecting portion 52 and the second connectingportion 53.

The covering member 70 is made of a fiber reinforced plastic (FRP: FiberReinforced Plastics). Preferably, the covering member 70 is made ofcarbon fiber reinforced plastic (CFRP: Carbon Fiber ReinforcedPlastics). Usable carbon fibers may include PAN-based carbon fibers andpitch-based carbon fibers. It may also be possible that the coveringmember 70 is made of, e.g., a glass fiber-reinforced plastic (GFRP), aglass-mat reinforced thermoplastic (GMT), a boron fiber-reinforcedplastic (BFRP), an aramid fiber-reinforced plastic (AFRP, KFRP), aDyneema fiber-reinforced plastic (DFRP), a Xyron-reinforced plastic(ZFRP), etc. Further, it may also be possible to use a fiber-reinforcedplastic including a plurality of types of fibers combined together or touse a plurality of types of fiber-reinforced plastics combined togetherto make the covering member 70.

The covering member 70 is a tow made of the same material andconstituted by a bundle of fiber bundles (filaments) including a largenumber of monofilaments. In addition, it may also be possible that thecovering member 70 is a monofilament, a filament, a staple yarn producedby staple spinning, or a braid or a knitted cord including tows. Thecovering member 70 is provided in layers by wrapping around the outersurfaces of the core shaft 60, the first connecting portion 52, and thesecond connecting portion 53. The covering member 70 is wound indifferent directions.

The material of the head 30 or the bush 40 is different from thematerial of the core shaft 60. That is, the core shaft core 60 is formedof a different material from the material of the head 30 and thematerial of the bush 40. The head 30 and the bush 40 are made of, forexample, a metal material. As the metal material used for the head 30and the bush 40, a titanium alloy, chrome-molybdenum steel,nickel-chrome-molybdenum steel, stainless steel, and any other knownmetal materials can be used. The head 30 and the bush 40 may be made ofa material other than the metal material. For example, the head 30 andthe bush 40 may be made of a ceramic material, a fiber-reinforcedplastic such as CFRP, or any other resin materials. The core shaft 60 isformed of a thermoplastic resin such as a polymer plastic so that thecore shaft becomes deformable and can be bent. As discussed above, thehead 30 or the bush 40 is made of a material different from that of thecore shaft 60. Any other resin materials or metal materials in additionto the polymer plastic may be used for the core shaft 60.

The head 30 bifurcates. The head 30 includes a first arm portion 33 anda second arm portion 34 to which the core shafts 60 and the bushes 40are connected. The head 30 has a first portion 31 including the firstarm portion 33 and a second portion 32 including the second arm portion34. The first portion 31 and the second portion 32 are separable fromeach other. The first arm portion 33 is connected to the first link mainbody 50A. The second arm portion 34 is connected to the second link mainbody 50B. The head 30 is fixed to the core shaft 60 with the coveringmember 70, and also fixed to the bush 40 with the covering member 70.Here, by providing the bifurcated portion in the head 30 of the reactionlink 20, the curvature of the link main body 50 is reduced.Consequently, it is possible to prevent the covering member 70 fromcreasing due to the bend.

A fitting structure is provided at a joining portion 37 between thefirst portion 31 and the second portion 32 of the head 30. The fittingstructure is a structure in which one of the first portion 31 or thesecond portion 32 of the head 30 is fitted into the other. The head 30is configured such that the fulcrum shaft 104 provided in the actuator10 penetrates the head 30. The joining portion 37 is provided in athrough-hole portion 38 through which the fulcrum shaft 104 penetrates.Due to the fitting structure, only one of the first portion 31 or thesecond portion 32 contacts the fulcrum shaft 104 which is the rotationshaft. Of the head 30, only the first portion 31 comes into contact withthe fulcrum shaft 104. The joining portion 37 includes a joining convexportion 37A and a joining concave portion 37B. The joining convexportion 37A is provided in the first portion 31. The joining concaveportion 37B is provided in the second portion 32, and the joining convexportion 37A contacts the joining concave portion 37B. A bearing may beprovided between the fulcrum shaft 104 and the joining portion 37.

As shown in FIGS. 6 and 7 , each of the first bush 40A and the secondbush 40B is connected to a second end portion 62 of the core shaft 60 atthe second connecting portion 53 and is covered with the covering member70. A base end of the bush 40 has a recess 42 into which the second endportion 62 of the core shaft 60 is inserted. The second end portion 62of the core shaft 60 is inserted into the recess 42 of the bush 40, andthe bush 40 and the core shaft 60 are connected to each other. That is,the first bush 40A and the second bush 40B each covers at leastpartially the second end portion 62 of the core shaft 60.

An outer diameter DB of the second end 62 of the core shaft 60 issmaller than an outer diameter D1 of the first bush 40A and the secondbush 40B (DB<D1). An outer peripheral surface of the bush 40 near thetip is provided with a wavy portion 43 formed in a wavy shape.Specifically, in the wavy portion 43 of the bush 40, a first ridgeportion 44 and a second ridge portion 45 extending in thecircumferential direction are formed. A recess 46 having an outerdiameter D3 is formed between the first ridge portion 44 and the secondridge portion 45. An outer diameter D1 of the first ridge portion 44 islarger than an outer diameter D2 of the second ridge portion 45 (D1>D2).An outer diameter D3 of the recess 46 is smaller than the outer diameterD1 of the first ridge portion 44 and the outer diameter D2 of the secondridge portion 45 (D3<D2<D1). The covering member 70 is provided tightlyon and along the outer surface of the bush 40 and the core shaft 60without any gap. Therefore, even if the bush 40 is pulled, the coveringmember 70 is caught by the first ridge portion 44 and the second ridgeportion 45 of the bush 40, and the core shaft 60 and the bush 40 remainconnected to each other without using fasteners or the like. Even if thebush 40 is further pulled and the second ridge portion 45 comes off fromthe covering member 70, the covering member 70 is caught by the firstridge portion 44 to prevent the entire bush 40 from completely comingoff from the covering member 70.

When the covering member 70 is made of a fiber reinforced plastic,moisture or the like may infiltrate the covering member 70 from a secondend portion 72 of the covering member 70 near the bush 40 along thefibers by capillary action. To prevent this, the second end portion 72of the covering member 70 is coated with a coating material 73 such asresin. By coating the second end portion 72 with the coating material73, it is possible to prevent the infiltration of moisture and the like.The coating material 73 is applied to the second end portion 72 to fixthe covering member 70 and the bush 40 thereto.

As shown in FIGS. 8 and 9 , the first portion 31 and the second portion32 of the head 30 are each connected to the first end portion 61 of thecore shaft 60 at the first connecting portion 52 and covered with thecovering member 70. The tip of the first arm portion 33 has a firstrecess 35 into which the first end portion 61 of the core shaft 60 isinserted. The first end portion 61 of the core shaft 60 is inserted inthe first recess 35, which joints the first arm portion 33 and the coreshaft 60. That is, the first portion 31 and the second portion 32 of thehead 30 partially cover the first end portion 61 of the core shaft 60.

An outer diameter DA of the first end portion 61 of the core shaft 60 issmaller than an outer diameter D4 of the first arm portion 33 and thesecond arm portion 34 (DA<D4). An outer peripheral surface of the firstarm portion 33 near the tip is provided with a wavy pattern.Specifically, the first ridge portion 33A and the second ridge portion33B extending in the circumferential direction are formed on the outerperipheral surface of the first arm portion 33 near the tip. A recess33C having an outer diameter D6 is formed between the first ridgeportion 33A and the second ridge portion 33B. An outer diameter D4 ofthe first ridge portion 33A is larger than an outer diameter D5 of thesecond ridge portion 33B (D4>D5). An outer diameter D6 of the recess 33Cis smaller than the outer diameter D4 of the first ridge portion 33A andthe outer diameter D5 of the second ridge portion 33B (D6<D5<D4). Thecovering member 70 is provided tightly on and along the outer surface ofthe first arm portion 33 and the core shaft 60 without any gap.Therefore, even if the head 30 is pulled, the covering member 70 iscaught by the first ridge portion 34A and the second ridge portion 34Bof the head 30, and the core shaft 60 and the head 30 remain connectedto each other without using fasteners or the like. Even if the secondridge portion 33B is pulled further and comes off from the coveringmember 70, the covering member 70 is caught by the first ridge portion33A to prevent the head 30 from completely coming off from the coveringmember 70. The tip of the second arm portion 34 has a second recess 36into which the core shaft 60 is inserted. The core shaft 60 is insertedin the second recess 36, which connects the second arm portion 34 andthe core shaft 60. An outer peripheral surface of the second arm portion34 near the tip is provided with a wavy pattern. Specifically, the firstridge portion 34A and the second ridge portion 34B are formed on theouter peripheral surface of the second arm portion 34 near the tip. Arecess 34C having an outer diameter D6 is formed between the first ridgeportion 34A and the second ridge portion 34B. An outer diameter D4 ofthe first ridge portion 34A is larger than an outer diameter D5 of thesecond ridge portion 34B (D4>D5). An outer diameter D6 of the recess 34Cis smaller than the outer diameter D4 of the first ridge portion 34A andthe outer diameter D5 of the second ridge portion 34B (D6<D5<D4). Thecovering member 70 is provided tightly on and along the outer surface ofthe second arm portion 34 and the core shaft 60 without any gap.Therefore, even if the head is pulled further and the second ridgeportion 34B comes off from the covering member 70, the covering member70 is caught by the first ridge portion 34A to prevent the head 30 fromcompletely coming off from the covering member 70.

When the covering member 70 is a fiber reinforced plastic, moisture orthe like may infiltrate the covering member 70 from a first end portion71 of the covering member 70 near the head 30 along the fibers bycapillary action. To prevent this, the first end portion 71 of thecovering member 70 is coated with the coating material 73 such as resin.By coating the first end portion 71 with the coating material 73, it ispossible to prevent the infiltration of moisture and the like. Thecoating material 73 is applied to the first end portion 71 to fix thecovering member 70 and the head 30 thereto. The resin used for thecoating material 73 is preferably the same as the resin impregnated withthe fibers of the fiber reinforced plastic because of its high affinity.

In the link main body 50, the head 30 and the bush 40 are connected bythe core shaft 60 made of resin and the covering member 70 made of fiberreinforced plastic, so that it is possible to reduce the weight whileensuring the required strength.

Next, a method of manufacturing the reaction link 20 will now bedescribed with reference to FIGS. 10 to 18 .

As shown in FIG. 10 , the manufacturing method of the reaction link 20includes a covering step (step S1), a connecting step (step S2), ajoining step (step S3), a bending step (step S4), a heating step (stepS5), and a coating step (step S6).

As shown in FIG. 11 , two or more core shafts 60 are connected to eachother by connecting jigs 90. The connecting jig 90 is further providedat each end of the core shaft 60. By doing so, it is possible tocollectively perform the covering work onto the two or more core shafts60. Not limited to the two core shafts 60, three or more core shafts 60may be connected by the connecting jigs 90.

As shown in FIG. 12 , in the following covering step of step S1, theplurality of the core shafts 60 connected by the connecting jigs 90 arecovered with the covering member 70. The covering member 70 is wound notonly around the core shafts 60 but also around the connecting jigs 90 inlayers. Specifically, an impregnation fluid tank containing athermosetting resin (e.g., unsaturated polyester) as an impregnationfluid is first prepared. Then, fibers extending from a winding machine(not shown) may be soaked into the impregnation fluid tank. The windingmachine is used for winding the fibers around the core shafts 60. As forthe impregnation fluid, the unsaturated polyester may be replaced with,e.g., an epoxy resin, a polyamide resin, or a phenol resin. Thethermosetting resin may be replaced with, e.g., a UV-curable resin, alight curable resin, a thermoplastic resin (e.g., methyl methacrylate).The fibers impregnated with the thermosetting resin are woven togetherand wound around the core shafts 60 by the winding machine. The fibersare wound in two layers around the first connecting portion 52, the coreshaft 60, and the second connecting portion 53. In the covering step,the link main body 50 is formed. The fibers are exposed at both ends ofthe covering member 70.

Subsequently, as shown in FIG. 12 , the covering member 70 is cut at theportions of the connecting jigs 90 that connect the core shafts 60 toeach other. Cutting may be performed only to the covering member 70.Alternatively, the connection jig 90 may also be cut. As shown in FIG.13 , the connection jig 90 at each end of the core shaft 60 is removed.

Subsequently, as shown in FIGS. 14 and 15 , in the connecting step ofstep S2, the first portion 31 of the head 30 is inserted into the tubeformed of the covering member 70 that covers the core shaft 60. Then,the first portion 31 of the head 30 is connected to the first endportion 61 of the core shaft 60. At the first connecting portion 52, thefirst end portion 61 of the core shaft 60 is inserted into the firstrecess 35 of the first arm portion 33 of the head 30. The first bush 40Ais inserted into the tube formed of the covering member 70 that coversthe core shaft 60. The first bush 40A is connected to the second endportion 62 of the core shaft 60. At the second connecting portion 53,the second end portion 62 of the core shaft 60 is inserted into therecess 42 of the first bush 40A. As discussed above, the covering member70 is wound in layers to cover from the first arm portion 33 of thefirst portion 31 to the wavy portion 43 of the first bush 40A.

Subsequently, as shown in FIGS. 16 and 17 , in the connecting step ofstep S2, the second portion 32 of the head 30 is inserted into the tubeformed of the covering member 70 that covers the core shaft 60. Then,the second portion 32 of the head 30 is connected to the first endportion 61 of the core shaft 60. At the first connecting portion 52, thefirst end portion 61 of the core shaft 60 is inserted into the secondrecess 36 of the second arm portion 34 of the head 30. The second bush40B is inserted into the tube formed of the covering member 70 thatcovers the core shaft 60. The second bush 40B is connected to the secondend portion 62 of the core shaft 60. At the second connecting portion53, the second end portion 62 of the core shaft 60 is inserted into therecess 42 of the second bush 40B. As discussed above, the coveringmember 70 is wound in layers from the second arm portion 34 of thesecond portion 32 to the wavy portion 43 of the second bush 40B.

Subsequently, as shown in FIGS. 4 and 5 , in the joining step of stepS3, the first portion 31 and the second portion 32 of the head 30 arejoined to each other. Specifically, the joining convex portion 37A ofthe first portion 31 is fitted into the joining concave portion 37B ofthe second portion 32. The first portion 31 and the second portion 32are then screwed to be fastened to each other.

Subsequently, as shown in FIG. 18 , in the bending step of step S4, thehead 30, the core shaft 60, and the bush 40 covered with the coveringmember 70 are placed on a jig 80. The core shaft 60 is bent at aposition different from the first connecting portion 52 between the head30 and the core shaft 60. Specifically, a head fixing shaft 81 forfixing the head 30 is inserted through the through hole portion 38 ofthe head 30, and the position of the head 30 is fixed. The reaction link20 is placed on the jig 80 in a state where the link main body 50extends in a straight line form as shown in FIGS. 15 and 17 . Then, abent portion fixing member 82 bends the link main body 50 by pressingthe central portion of the link main body 50. The bent portion fixingmember 82 pushes the link main body 50 to a position where the pair oflink main bodies 50 extend parallel to each other and fixes them at thatposition. When the pair of link main bodies 50 become parallel to eachother, a bush fixing shaft 83 is inserted through the through holes 41of both bushes 40 to fix the pair of bushes 40 at that position. Here,the position where the link main body 50 bends is different from theposition of the first connecting portion 52 between the head 30 and thecore shaft 60. Thus, it is possible to prevent the fiber reinforcedplastic, which is the covering member 70, from creasing. This creasingprevention way is particularly effective when the first connectingportion 52 is provided with the wavy pattern that prevents the componentfrom coming off.

As shown in FIG. 18 , in the heating step of step S5, the coveringmember 70 is cured by heating. The reaction link 20 fixed to the jig 80is placed in a vacuum chamber and heated. The covering member 70 iscured by heating. When an ultraviolet curable resin is used instead ofthe thermosetting resin as the impregnating fluid, the resin impregnatedin the fibers is cured by irradiating the link main body 50 withultraviolet rays in the heating step.

Subsequently, as shown in FIG. 4 , in the coating step of step S6, thecoating material 73 is applied to the head 30 and the bush 40 so as tocover the first end portion 71 and the second end portion 72 of thecovering member 70.

The action of the reaction link 20 will now be described with referenceto FIG. 2 .

As shown in FIG. 2 , when a reaction force produced when the actuator 10drives the flight control surface 101 is imparted to the actuator 10,the bush 40 may be subjected to a tensile load, a compressive load, or atorsional load via the shaft 13A connecting between the actuator 10 andthe reaction link 20. The covering member 70 covers the first connectingportion 52 and the second connecting portion 53. Further, the coveringmember 70 is wound around the link main body 50 continuously from thehead 30 to the bush 40. Thus, the covering member 70 receives a forcewhen a tensile load, a compressive load, or a torsional load is appliedto the bush 40. Therefore, the weight of the link main body 50 can bereduced while maintaining the strength required for the reaction link20. Further, even if water drops on the reaction link 20 due to a changein atmospheric pressure or the like, the end portion of the coveringmember 70 is covered with the coating material 73, so that it ispossible to prevent water or the like from entering into the coveringmember 70. At the through hole portion 38 of the head 30, only thejoining convex portion 37A of the first portion 31 contacts the shaft13A of the connecting portion 13, and the joining convex portion 37Acontacts the joining concave portion 37B. Therefore, even if the firstportion 31 or the second portion 32 of the head 30 and the core shaft 60are broken, the connected state between the head 30 and the shaft 13Acan be maintained and the load support can be maintained.

The following describes advantageous effects of the embodiment.

(1) The joint structure includes the covering member 70 that is made ofa fiber reinforced plastic and that tightly covers the shaft coreportion 60, the first ridge portion 34A and the second ridge portion 34Bof the head 30, and the first ridge portion 44 and the second ridgeportion 45 of the bush 40. Since the covering material 70 is providedtightly around the first ridge portion 34A and the second ridge portion34B of the head 30 and the first ridge portion 44 and the second ridgeportion 45 of the bush 40, the covering material 70 is caught by thefirst ridge portion 34A and the second ridge portion 34B of the head 30and the first ridge portion 44 and the second ridge portion 45 of thebush 40. Therefore, the core shaft 60, the head 30, and the bush 40 canbe connected without using a fastener.

(2) The outer diameters of the two ridge portions, that is, the outerdiameter D3 of the first ridge portion 33A or 34A and the outer diameterD4 of the second ridge portion 33B or 34B increases toward the tip ofthe head 30. That is, the closer the portion of each ridge portion issituated to the tip of the head 30, the larger the outer diameter of theridge portion becomes. Therefore, even if the head 30 is pulled and thefirst ridge portion 33A or 34A comes off from the covering member 70,the covering member 70 is caught by the second ridge portion 33B or 34Bto prevent the head 30 from completely coming off from the coveringmember 70. The outer diameters of the two ridge portions, that is, theouter diameter D1 of the first ridge portion 44A and the outer diameterD2 of the second ridge portion 45 increases toward the tip of the bush40. That is, the closer the portion of each ridge portion is situated tothe tip of the bush 40, the larger the outer diameter of the ridgeportion becomes. Therefore, even if the bush 40 is pulled and the firstridge portion 44A comes off from the covering member 70, the coveringmember 70 is caught by the second ridge portion 45B to prevent the bush40 from completely coming off from the covering member 70.

(3) At the first connecting portion 52, the head 30 covers at least apart of the end portion of the shaft core portion 60. Therefore it ispossible to enhance bonding between the core shaft 60 and the head 30 bythe covering member 70 tightly provided on the head 30 that covers theend portion of the core shaft 60. At the second connecting portion 53,the bush 40 covers at least a part of the end portion of the shaft coreportion 60. Therefore it is possible to enhance bonding between the coreshaft 60 and the bush 40 by the covering member 70 tightly provided onthe bush 40 that covers the end portion of the core shaft 60.

(4) By covering the first end portion 71 and the second end portion 72of the covering member 70, which is a fiber reinforced plastic, with thecoating material 73, which is a resin, it is possible to preventmoisture and the like from infiltrating into the fiber reinforcedplastic.

(5) The head 30 can separate into the first portion 31 and the secondportion 32. Thus, the first portion 31 and the second portion 32 areseparately joined to the corresponding core shaft 60 and thecorresponding bush 40 and then they are fixed to each other by thecovering member 70. Thereafter, the first portion 31 and the secondportion 32 can be combined. In this way, the head 30, the core shaft 60,and the bush 40 can be easily placed on a tool such as the jig.

Other Embodiments

The foregoing embodiments can be modified as described below. The aboveembodiment and the following modifications can be implemented incombination to the extent where they are technically consistent to eachother.

-   -   In the above embodiment, the first end portion 71 of the        covering member 70 is coated with the coating material 73 such        as resin. Alternatively, the first end portion 71 of the        covering member 70 may not be covered with a coating material        such as resin.    -   In the above embodiment, the second end portion 72 of the        covering member 70 is coated with the coating material 73 such        as resin. Alternatively, the second end portion 72 of the        covering member 70 may not be covered with a coating material        such as resin.    -   In the above embodiment, the head 30 covers the end portion of        the core shaft 60 at least partially. Alternatively, the head 30        may not cover the end portion of the core shaft 60.    -   In the above embodiment, the bush 40 covers the end portion of        the core shaft 60 at least partially. Alternatively, the bush 40        may not cover the end portion of the core shaft 60.    -   In the above embodiment, two ridges, that is, the first ridge        33A or 34A and the second ridge 33B or 34B are provided on the        outer peripheral surface of the head 30. Alternatively, three or        more ridges may be provided on the outer peripheral surface of        the head 30. The outer diameter of these ridges may increase        toward the tip of the head 30. Alternatively, only one ridge may        be provided on the outer peripheral surface of the head 30.    -   In the above embodiment, two ridges, that is, the first ridge 44        and the second ridge 45 are provided on the outer peripheral        surface of the bush 40. Alternatively, three or more ridges may        be provided on the outer peripheral surface of the bush 40. The        outer diameter of these ridges may increase toward the tip of        the bush 40. Alternatively, only one ridge may be provided on        the outer peripheral surface of the bush 40.    -   In the above embodiment, the shape and outer diameter of the        second connecting portion 53 are the same between the first bush        40A and the second bush 40B. Alternatively, at least one of the        shape or the outer diameter of the second connecting portion 53        may be made different between the first bush 40A and the second        bush 40B.    -   In the above embodiment, the shape and outer diameter of the        first connecting portion 52 are the same between the first arm        portion 33 and the second arm portion 34. Alternatively, at        least one of the shape or the outer diameter of the first        connecting portion 52 may be made different between the first        arm portion 33 and the second arm portion 34.    -   In the above embodiment, after the covering step (step S1) of        covering the core shaft 60 with the covering material 70, the        connecting step (step S2) of connecting the head 30 and the bush        40 to the link main body 50 is performed. Alternatively, after        the connecting step (new step S1) of connecting the head 30 and        the bush 40 to the core shaft 60, the covering step (new step        S2) of covering the core shaft 60, the head 30, and the bush 40        with the covering material 70 may be performed. The joining step        of the head 30 is performed after the covering step. That is, as        shown in FIGS. 19 and 20 , in the connecting step of step S1,        the first portion 31 of the head 30 is connected to the first        end portion 61 of the core shaft 60. At the first connecting        portion 52, the first end portion 61 of the core shaft 60 is        inserted into the first recess 35 of the first arm portion 33 of        the head 30. The first bush 40A is connected to the second end        portion 62 of the core shaft 60. At the second connecting        portion 53, the second end portion 62 of the core shaft 60 is        inserted into the recess 42 of the first bush 40A. Subsequently,        as shown in FIGS. 15 and 17 , in the covering step of step S2,        the first connecting portion 52 between the head 30 and the core        shaft 60 and the second connecting portion 53 between the bush        40 and the core shaft 60 are covered with the covering member        70. As discussed above, the covering member 70 is wound in        layers from the first arm portion 33 of the first portion 31 to        the wavy portion 43 of the first bush 40A. Similarly, the        covering member 70 is wound in layers from the second arm        portion 34 of the second portion 32 to the wavy portion 43 of        the second bush 40B.    -   In the above embodiment, the shape of the ridge portion may have        any shape such as a semicircle cross section, a square cross        section, and a triangle cross section. Further, convex or        hemisphere patterns may be provided on the outer periphery of        the head 30 and the bush 40 at intervals.    -   Only the first portion 31 of the head contacts the fulcrum shaft        104 in the above embodiment. Alternatively, only the second        portion 32 contacts the fulcrum shaft 104. Alternatively, both        the first portion 31 and the second portion 32 may contact the        fulcrum shaft 104.    -   In the above embodiment, the first portion 31 and the second        portion 32 of the head 30 are joined by the fitting structure at        the joining portion 37. Alternatively, the joining portion 37        may not have the fitting structure.    -   In the above embodiment, the head 30 is configured to be        separated into the first portion 31 and the second portion 32.        Alternatively, the first portion 31 and the second portion 32        may be integrated and form a single body.    -   In the above embodiment, the head 30 and the bush 40 are made of        a material(s) different from that of the core shaft 60.        Alternatively, the head 30, the bush 40, and the core shaft 60        may be made of the same material.    -   In the above embodiment, the first member rotatably connected to        the mating member and the second member rotatably connected to        the actuator for driving the mating member may be any members        other than the head 30 and the bush 40.    -   In the above embodiment, the fibers may be wound around the core        shaft 60 in the coating step and then impregnated in the        impregnating liquid tank. Alternatively, to impregnate the        resin, the fibers may be sprayed with a thermosetting resin, a        UV-curable resin, a light curable resin, or a thermoplastic        resin, instead of being soaked into the fluid tank.

The foregoing embodiments describe a plurality of physically separateconstituent parts. They may be combined into a single part, and any oneof them may be divided into a plurality of physically separateconstituent parts. Irrespective of whether or not the constituent partsare integrated, they are acceptable as long as they are configured tosolve the problems.

What is claimed is:
 1. A joint structure, comprising: a first memberconfigured to be connected rotatably to a mating member, the firstmember having one or more ridge portions that extend circumferentiallyalong an outer peripheral surface; a second member configured to beconnected rotatably to an actuator for driving the mating member, thesecond member having one or more ridge portions that extendcircumferentially along an outer peripheral surface; a core shaftconnecting the first member and the second member; and a covering memberprovided tightly thereon to cover the core shaft, the one or more ridgeportions of the first member, and the one or more ridge portions of thesecond member.
 2. The joint structure of claim 1, wherein the one ormore ridges of at least one of the first member or the second memberinclude two or more ridges portions, and wherein an outer diameter ofeach of the ridge portions increases toward a tip of the at least one ofthe first member of the second member.
 3. The joint structure of claim1, wherein at least one of the first member or the second member coversat least partially an end portion of the core shaft.
 4. The jointstructure of claim 1, wherein the covering member is made of a fiberreinforced plastic, and wherein an end portion of the fiber reinforcedplastic is coated with a resin.
 5. A method of manufacturing a jointstructure that includes a first member configured to be connectedrotatably to a mating member, the first member having one or more ridgeportions that extend circumferentially along an outer peripheralsurface; a second member configured to be connected rotatably to anactuator for driving the mating member, the second member having one ormore ridge portions that extend circumferentially along an outerperipheral surface; a core shaft having a first end portion and a secondend portion, and a covering member provided tightly thereon to cover thecore shaft, the one or more ridge portions of the first member, and theone or more ridge portions of the second member, the method comprising:covering an outer peripheral surface of the core shaft with the coveringmember; inserting the first member into the covering member to connectthe first member to the first end portion and inserting the secondmember into the covering member to connect the second member to thesecond end portion; and heating the covering member to cure while thecovering member tightly contacts the core shaft, the one or more ridgeportions of the first member, and the one or more ridge portions of thesecond member.
 6. The method of claim 5, wherein the core shaft is oneof a pair of the core shafts, the second member is one of a pair of thesecond members, and the covering member is one of a pair of the coveringmembers, wherein the first member has a first portion including a firstarm portion and a second portion including a second arm portion, thefirst member bifurcates into the first arm portion and the second armportion, wherein the first arm portion and the second arm portion areeach connected to a corresponding one of the pair of core shafts and acorresponding one of the pair of second members, and wherein the methodfurther includes joining the first portion and the second portiontogether after the connecting.